Caloric Water Heater Appliance

ABSTRACT

A water heater appliance includes a first heat exchanger that is coupled to a tank. The water heater appliance also includes a caloric heat pump system that is configured for heating liquid within the tank via the first heat exchanger. The caloric heat pump system includes a plurality of caloric material stages. A field generator is positioned such that the caloric material stages are moved in and out of a field of the field generator during operation of the caloric heat pump system.

FIELD OF THE INVENTION

The present subject matter relates generally to water heater appliances, such as heat pump water heater appliances

BACKGROUND OF THE INVENTION

Heat pump water heaters are gaining broader acceptance as a more economic and ecologically-friendly alternative to electric water heaters. Heat pump water heaters include a sealed system for heating water to the set temperature. Conventional sealed system technology typically utilizes a heat pump that relies on compression and expansion of a fluid refrigerant to receive and reject heat in a cyclic manner so as to effect a desired temperature change or i.e. transfer heat energy from one location to another. This cycle can be used to provide e.g., for the receiving of heat from the environment and the rejecting of such heat to a tank of water. A variety of different fluid refrigerants have been developed that can be used with the heat pump in such systems.

While improvements have been made to such heat pump systems that rely on the compression of fluid refrigerant, at best such can still only operate at about forty-five percent or less of the maximum theoretical Carnot cycle efficiency. Also, some fluid refrigerants have been discontinued due to environmental concerns. The range of ambient temperatures over which certain refrigerant-based systems can operate may be impractical for certain locations. Other challenges with heat pumps that use a fluid refrigerant exist as well.

Accordingly, a water heater appliance with features for efficiently heating water within the water heater appliance would be useful. In particular, a water heater appliance with features for efficiently heating water without requiring compression of fluid refrigerant would be useful.

BRIEF DESCRIPTION OF THE INVENTION

The present subject matter provides a water heater appliance. A first heat exchanger is coupled to a tank, and a caloric heat pump system is configured for heating liquid within the tank via the first heat exchanger. The caloric heat pump system includes a plurality of caloric material stages. A field generator is positioned such that the caloric material stages are moved in and out of a field of the field generator during operation of the caloric heat pump system. Additional aspects and advantages of the invention will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice of the invention.

In a first exemplary embodiment, a water heater appliance is provided. The water heater appliance includes a tank. A first heat exchanger is coupled to the tank for delivery of heat to liquid within the tank. The water heater appliance also includes a second heat exchanger. A caloric heat pump system is configured for heating liquid within the tank via the first heat exchanger. The caloric heat pump system includes a plurality of caloric material stages. A field generator is positioned proximate the caloric material stages. The field generator is positioned such that the caloric material stages are sequentially moved in and out of a field of the field generator during operation of the caloric heat pump system. The caloric heat pump system further includes a pump for circulating a heat transfer fluid between the first and second heat exchangers and the caloric material stages.

In a second exemplary embodiment, a water heater appliance is provided. The water heater appliance includes a casing. A tank is disposed within the casing. A first heat exchanger is disposed within the casing and is coupled to the tank for delivery of heat to liquid within the tank. A second heat exchanger is also disposed within the casing such that the second heat exchanger is spaced apart from the first heat exchanger. A caloric heat pump system is disposed within the casing and is configured for heating liquid within the tank via the first heat exchanger. The caloric heat pump system includes a plurality of caloric material stages. A field generator is positioned proximate the caloric material stages. The field generator is positioned such that the caloric material stages are moved in and out of a field of the field generator during operation of the caloric heat pump system. The caloric heat pump system also includes a pump for circulating an aqueous heat transfer fluid between the first and second heat exchangers and the caloric material stages.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures.

FIG. 1 provides a perspective view of a water heater appliance according to an exemplary embodiment of the present subject matter.

FIG. 2 provides a schematic view of certain components of the exemplary water heater appliance of FIG. 1.

FIG. 3 provides a perspective view of a heat pump according to an exemplary embodiment of the present subject matter.

FIG. 4 provides an exploded view of the exemplary heat pump of FIG. 3.

FIG. 5 provides a section view of the exemplary heat pump of FIG. 3.

FIG. 6 provides perspective view of the exemplary heat pump of FIG. 3.

FIG. 7 provides a schematic representation of various steps in the use of a stage of the exemplary heat pump of FIG. 3.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

The present subject matter is directed to a water heater appliance with a caloric heat pump system for heating water within the water heater appliance. While described in greater detail below in the context of a magneto-caloric heat pump system, one of skill in the art will recognize that other suitable caloric materials may be used in a similar manner to heat water within the water heater appliance, i.e., apply a field, move heat, remove the field, move heat. For example, electro-caloric material heats up and cools down within increasing and decreasing electric fields. As another example, elasto-caloric material heats up and cools down when exposed to increasing and decreasing mechanical strain. As yet another example, baro-caloric material heats up and cools down when exposed to increasing and decreasing pressure. Such materials another other similar caloric materials may be used in place of or in addition to the magneto-caloric material described below to heat water within the water heater appliance. Thus, caloric material is used broadly herein to encompass materials that undergo heating or cooling when exposed to a changing field from a field generator, where the field generator may be an electric field generator, an actuator for applying mechanical stress or pressure, etc.

FIG. 1 provides a perspective view of a water heater appliance 100 according to an exemplary embodiment of the present subject matter. It should be understood that water heater appliance 100 is provided by way of example only and that the present subject matter may be used in or with any suitable water heater appliance. Thus, other configurations for water heater appliance different from that shown in FIGS. 1 and 2 may be used with the present subject matter as well.

Water heater appliance 100 includes a casing 102. A tank 112 (FIG. 2) is mounted within casing 102. Tank 112 defines an interior volume 114 for heating water therein. Water heater appliance 100 also includes a cold water conduit 104 and a hot water conduit 106 that are both in fluid communication with tank 112 within casing 102. As an example, cold water from a water source, e.g., a municipal water supply or a well, enters water heater appliance 100 through cold water conduit 104. From cold water conduit 104, such cold water enters interior volume 114 of tank 112 wherein the water is heated to generate heated water. Such heated water exits water heater appliance 100 at hot water conduit 106 and, e.g., is supplied to a bath, shower, sink or any other suitable feature.

As may be seen in FIG. 1, water heater appliance 100 extends between a top portion 108 and a bottom portion 109 along a vertical direction V. Thus, water heater appliance 100 is generally vertically oriented. Water heater appliance 100 can be leveled, e.g., such that casing 102 is plumb in the vertical direction V, in order to facilitate proper operation of water heater appliance 100. A drain pan 110 is positioned at bottom portion 109 of water heater appliance 100 such that water heater appliance 100 sits on drain pan 110. Drain pan 110 sits beneath water heater appliance 100 along the vertical direction V, e.g., to collect water that leaks from water heater appliance 100 or water that condenses on a second heat exchanger 128 of water heater appliance 100.

FIG. 2 provides a schematic view of certain components of water heater appliance 100 including an interior volume 114 of a tank 112 and a machinery compartment 140. Machinery compartment 140 may be positioned above tank 112 within casing 102 (FIG. 1). As shown in FIG. 2, water heater appliance 100 includes an upper heating element 118, a lower heating element 119 and a heat pump system 120 for heating water within interior volume 114 of tank 112. Upper and lower heating elements 118 and 119 can be any suitable heating elements. For example, upper heating element 118 and/or lower heating element 119 may be an electric resistance element, a microwave element, an induction element, or any other suitable heating element or combination thereof. Lower heating element 119 may also be a gas burner. Upper and lower heating elements 118 and 119 may be mounted to and positioned within tank 112, as shown in FIG. 2.

Heat pump system 120 includes a pump 122, a first heat exchanger 124, a heat pump 126 and a second heat exchanger 128. Various components of heat pump system 120 may be positioned within casing 102, including pump 122, first heat exchanger 124, heat pump 126 and second heat exchanger 128. In particular, pump 122, heat pump 126 and second heat exchanger 128 may be positioned within machinery compartment 140 above tank 112, while first heat exchanger 124 is positioned on or at tank 112 below machinery compartment 140.

First heat exchanger 124 is assembled in a heat exchange relationship with tank 112 in order to heat water within interior volume 114 of tank 112 during operation of heat pump system 120. Thus, first heat exchanger 124 may be positioned at or adjacent interior volume 114 of tank 112 for the addition of heat thereto. A heat transfer fluid such as e.g., an aqueous solution, flowing within first heat exchanger 124 rejects heat to tank 112 and/or interior volume 114 of tank 112 thereby heating its contents. As an example, first heat exchanger 124 may be a conduit, such as copper or aluminum tubing, wound around tank 112 at an outer surface 180 of tank 112. When first heat exchanger 124 is a conduit wound around tank 112, first heat exchanger 124 may be brazed, soldered or otherwise suitably mounted to tank 112 at outer surface 180 of tank 112.

First heat exchanger 124 extends between an inlet 170 and an outlet 172. The heat transfer fluid from heat pump 126 may enter first heat exchanger 124 at inlet 170 of first heat exchanger 124, and the heat transfer fluid may exit first heat exchanger 124 at outlet 172 of first heat exchanger 124. Inlet 170 of first heat exchanger 124 may be positioned at or proximate bottom portion 109 of tank 112. Conversely, outlet 172 of first heat exchanger 124 may be positioned at or proximate top portion 108 of tank 112. Thus, inlet 170 of first heat exchanger 124 may be positioned below outlet 172 of first heat exchanger 124 along the vertical direction V on tank 112. In such a manner, the heat transfer fluid within first heat exchanger 124 may first heat relatively cool water at bottom portion 109 of tank 112 before flowing upwardly along the vertical direction V to heat relatively hot water at top portion 108 of tank 112. In such a manner, efficient heat transfer between the heat transfer fluid within first heat exchanger 124 and water within interior volume 114 of tank 112 may be facilitated.

First heat exchanger 124 may be wound around tank 112 between inlet and outlet 170, 172 of first heat exchanger 124. As an example, first heat exchanger 124 may be wound around tank 112 such that adjacent windings of first heat exchanger 124 are spaced apart from one another along the vertical direction V on outer surface 180 of tank 112, as shown in FIG. 2. In particular, adjacent windings of first heat exchanger 124 may be uniformly spaced apart from one another along the vertical direction V by a pitch P on outer surface 180 of tank 112. Thus, first heat exchanger 124 may be wound onto outer surface 180 of tank 112 at a constant rate. First heat exchanger 124 may be wound onto outer surface 180 of tank 112 at any suitable constant rate, such as e.g., about six windings per foot of tank 112 along the vertical direction V. By uniformly spacing adjacent windings of first heat exchanger 124 on outer surface 180 of tank 112, uniform heat transfer between the heat transfer fluid within first heat exchanger 124 and water within interior volume 114 of tank 112 along the vertical direction V may be facilitated.

After heating water within tank 112, the heat transfer fluid flows out of first heat exchanger 124 by line 160 to heat pump 126. As will be further described herein, the heat transfer fluid rejects additional heat to magneto-caloric material (MCM) in heat pump 126 and then flows by line 162 to second heat exchanger 128, e.g., that is disposed within machinery compartment 140. The heat transfer fluid within second heat exchanger 128 is heated by the environment, machinery compartment 140, and/or another location external to interior volume 114 of tank 112 via second heat exchanger 128. A fan 132 may be used to create a flow of air across second heat exchanger 128 and thereby improve the rate of heat transfer from the environment.

From second heat exchanger 128, the heat transfer fluid returns by line 164 to pump 122 and then to heat pump 126 where, as will be further described below, the heat transfer fluid receives heat from the MCM in heat pump 126. The now hotter heat transfer fluid flows by line 166 to first heat exchanger 124 to reject heat to tank 112 and/or interior volume 114 of tank 112 and repeat the cycle as just described. Pump 122 connected into line 164 causes the heat transfer fluid to circulate in heat pump system 120. Motor 130 is in mechanical communication with heat pump 126 as will further described. During operation of heat pump system 120, the heat transfer fluid may not undergo a phase change.

Heat pump system 120 is provided by way of example only. Other configurations of heat pump system 120 may be used as well. For example, lines 160, 162, 164 and 166 provide fluid communication between the various components of heat pump system 120 but other heat transfer fluid recirculation loops with different lines and connections may also be employed. For example, pump 122 can also be positioned at other locations or on other lines in heat pump system 120. Still other configurations of heat pump system 120 may be used as well. Heat pump 126 may be any suitable heat pump with MCM. For example, heat pump 126 may be constructed or arranged in the manner described in U.S. Patent Publication No. 2014/0165594 of Michael Alexander Benedict, which is hereby incorporated by reference in its entirety.

Water heater appliance 100 also includes a temperature sensor 116. Temperature sensor 116 is configured for measuring a temperature of water within interior volume 114 of tank 112. Temperature sensor 116 can be positioned at any suitable location within water heater appliance 100. For example, temperature sensor 116 may be positioned within interior volume 114 of tank 112 or may be mounted to tank 112 outside of interior volume 114 of tank 112. When mounted to tank 112 outside of interior volume 114 of tank 112, temperature sensor 116 can be configured for indirectly measuring the temperature of water within interior volume 114 of tank 112. For example, temperature sensor 116 can measure the temperature of tank 112 and correlate the temperature of tank 112 to the temperature of water within interior volume 114 of tank 112. Temperature sensor 116 can be any suitable temperature sensor. For example, temperature sensor 116 may be a thermocouple or a thermistor.

Water heater appliance 100 further includes a controller 150 that is configured for regulating operation of water heater appliance 100. Controller 150 is in, e.g., operative, communication with upper and lower heating elements 118 and 119, pump 122, motor 130, fan 132 and temperature sensor 116. Thus, controller 150 can selectively activate upper and lower heating elements 118 and 119 and/or pump 122 and motor 130 in order to heat water within interior volume 114 of tank 112.

Controller 150 includes memory and one or more processing devices such as microprocessors, CPUs or the like, such as general or special purpose microprocessors operable to execute programming instructions or micro-control code associated with operation of water heater appliance 100. The memory can represent random access memory such as DRAM, or read only memory such as ROM or FLASH. The processor executes programming instructions stored in the memory. The memory can be a separate component from the processor or can be included onboard within the processor. Alternatively, controller 150 may be constructed without using a microprocessor, e.g., using a combination of discrete analog and/or digital logic circuitry (such as switches, amplifiers, integrators, comparators, flip-flops, AND gates, and the like) to perform control functionality instead of relying upon software.

Controller 150 can operate upper heating element 118, lower heating element 119 and/or pump 122 and motor 130 in order to heat water within interior volume 114 of tank 112. As an example, a user can select or establish a set-point temperature for water within interior volume 114 of tank 112, or the set-point temperature for water within interior volume 114 of tank 112 may be a default value. Based upon the set-point temperature for water within interior volume 114 of tank 112, controller 150 can selectively activate upper heating element 118, lower heating element 119 and/or compressor 122 and motor 130 in order to heat water within interior volume 114 of tank 112 to the set-point temperature for water within interior volume 114 of tank 112. The set-point temperature for water within interior volume 114 of tank 112 can be any suitable temperature. For example, the set-point temperature for water within interior volume 114 of tank 112 may be between about one hundred degrees Fahrenheit and about one hundred and eighty-degrees Fahrenheit.

FIGS. 3 through 6 depict various views of an exemplary heat pump 200 of as may be used with the present subject matter. Thus, heat pump 200 may be utilized within water heater appliance 100 as heat pump 126. Heat pump 200 is provided by way of example only and is not intended to limit the present subject matter to any particular heat pump. As will be understood, any other suitable heat pump, such as a linearly actuating heat pump, may be utilized within water heater appliance 100 as heat pump 126 in alternative exemplary embodiments.

Heat pump 200 includes a regenerator housing 202 that extends longitudinally along an axial direction between a first end 218 and a second end 220. The axial direction is defined by axis A-A about which regenerator housing 202 is rotatable. A radial direction R is defined by a radius extending orthogonally from the axis of rotation A-A (FIG. 5). A circumferential direction is indicated by arrows C.

Regenerator housing 202 defines a plurality of chambers 204 that extend longitudinally along the axial direction defined by axis A-A. Chambers 204 are positioned proximate or adjacent to each other along circumferential direction C. Each chamber 204 includes a pair of openings 206 and 208 positioned at opposing ends 218 and 220 of regenerator housing 202.

Heat pump 200 also includes a plurality of stages 212 that include MCM. Each stage 212 is located in one of the chambers 204 and extends along the axial direction. For the exemplary embodiment shown in the figures, heat pump 200 includes eight stages 212 positioned adjacent to each other along the circumferential direction as shown and extending longitudinally along the axial direction. As will be understood by one of skill in the art using the teachings disclosed herein, a different number of stages 212 other than eight may be used as well.

A pair of valves 214 and 216 is attached to regenerator housing 202 and rotates therewith along circumferential direction C. More particularly, a first valve 214 is attached to first end 218 and a second valve 216 is attached to second end 220. Each valve 214 and 216 includes a plurality of apertures 222 and 224, respectively. For this exemplary embodiment, apertures 222 and 224 are configured as circumferentially-extending slots that are spaced apart along circumferential direction C. Each aperture 222 is positioned adjacent to a respective opening 206 of a chamber 204. Each aperture 224 is positioned adjacent to a respective opening 208 of a chamber 204. Accordingly, a heat transfer fluid may flow into a chamber 204 through a respective aperture 222 and opening 206 so as to flow through the MCM in a respective stage 212 and then exit through opening 208 and aperture 224. A reverse path can be used for flow of the heat transfer fluid in the opposite direction through the stage 212 of a given chamber 204.

Regenerator housing 202 defines a cavity 228 that is positioned radially inward of the plurality of chambers 204 and extends along the axial direction between first end 218 and second end 220. A magnetic element 226 is positioned within cavity 228 and, for this exemplary embodiment, extends along the axial direction between first end 218 and second end 220. Magnetic element 226 provides a magnetic field that is directed radially outward as indicated by arrows M in FIG. 5.

The positioning and configuration of magnetic element 226 is such that only a subset of the plurality of stages 212 is within magnetic field M at any one time. For example, as shown in FIG. 5, stages 212 a and 212 e are partially within the magnetic field while stages 212 b, 212 c, and 212 d are fully within the magnetic field M created by magnetic element 226. Conversely, the magnetic element 226 is configured and positioned so that stages 212 f, 212 g, and 212 h are completely or substantially out of the magnetic field created by magnetic element 226. However, as regenerator housing 202 is continuously rotated along the circumferential direction as shown by arrow W, the subset of stages 212 within the magnetic field will continuously change as some stages 212 will enter magnetic field M and others will exit.

A pair of seals 236 and 238 is provided with the seals positioned in an opposing manner at the first end 218 and second end 220 of regenerator housing 202. First seal 236 has a first inlet port 240 and a first outlet port 242 and is positioned adjacent to first valve 214. As shown, ports 240 and 242 are positioned 180 degrees apart about the circumferential direction C of first seal 214. However, other configurations may be used. For example, ports 240 and 242 may be positioned within a range of about 170 degrees to about 190 degrees about the circumferential direction C as well. First valve 214 and regenerator housing 202 are rotatable relative to first seal 236. Ports 240 and 242 are connected with lines 160 and 162 (FIG. 2), respectively. As such, the rotation of regenerator housing 202 about axis A-A sequentially places lines 160 and 162 in fluid communication with at least two stages 212 of MCM at any one time as will be further described.

Second seal 238 has a second inlet port 244 and a second outlet port 246 and is positioned adjacent to second valve 216. As shown, ports 244 and 246 are positioned 180 degrees apart about the circumferential direction C of second seal 216. However, other configurations may be used. For example, ports 244 and 246 may be positioned within a range of about 170 degrees to about 190 degrees about the circumferential direction C as well. Second valve 216 and regenerator housing 202 are rotatable relative to second seal 238. Ports 244 and 246 are connected with lines 166 and 164 (FIG. 2), respectively. As such, the rotation of regenerator housing 202 about axis A-A sequentially places lines 164 and 166 in fluid communication with at least two stages 212 of MCM at any one time as will be further described. Notably, at any one time during rotation of regenerator housing 202, lines 162 and 166 will each be in fluid communication with at least one stage 212 while lines 160 and 164 will also be in fluid communication with at least one other stage 212 located about 180 degrees away along the circumferential direction.

FIG. 7 illustrates an exemplary method using a schematic representation of stage 212 of MCM in regenerator housing 202 as it rotates in the direction of arrow W between positions 1 through 8 as shown in FIG. 6. As will be understood, other suitable arrangements of heat pump 126 (e.g., linear motion of stages 212 of MCM) may be utilized to provide similar heating and cooling of the heat transfer fluid, e.g., via the magneto-caloric effect in stages 212 of MCM. During step 700, stage 212 is fully within magnetic field M, which causes the magnetic moments of the material to orient and the MCM to heat as part of the magneto-caloric effect. Ordering of the magnetic field is created and maintained as stage 212 is rotated sequentially through positions 2, 3, and then 4 (FIG. 6) as regenerator housing 202 is rotated in the direction of arrow W. During the time at positions 2, 3, and 4, the heat transfer fluid dwells in the MCM of stage 212 and, therefore, is heated. More specifically, the heat transfer fluid does not flow through stage 212 because the openings 206, 208, 222, and 224 corresponding to stage 212 in positions 2, 3, and 4 are not aligned with any of the ports 240, 242, 244, or 246.

In step 702, as regenerator housing 202 continues to rotate in the direction of arrow W, stage 212 will eventually reach position 5. As shown in FIGS. 3 and 6, at position 5 the heat transfer fluid can flow through the material as first inlet port 240 is now aligned with an opening 222 in first valve 214 and an opening 206 at the first end 218 of stage 212 while second outlet port 246 is aligned with an opening 224 in second valve 216 at the second end 220 of stage 212. As indicated by arrow Q_(H-OUT), heat transfer fluid in stage 212, now heated by the MCM, can travel out of regenerator housing 202 and along line 166 to the first heat exchanger 124. At the same time, and as indicated by arrow Q_(H-IN), heat transfer fluid from second heat exchanger 128 flows into stage 212 from line 164 when stage 212 is at position 5. Because heat transfer fluid from the second heat exchanger 128 is relatively cooler than the MCM in stage 212, the MCM rejects heat to the heat transfer fluid.

Referring again to FIG. 7 and step 704, as regenerator housing 202 continues to rotate in the direction of arrow W, stage 212 is moved sequentially through positions 6, 7, and 8 where stage 212 is completely or substantially out of magnetic field M. The absence or lessening of the magnetic field is such that the magnetic moments of the material become disordered and the MCM absorbs heat as part of the magneto-caloric effect. During the time in positions 6, 7, and 8, the heat transfer fluid dwells in the MCM of stage 212 and, therefore, is cooled by losing heat to the MCM as the magnetic moments disorder. More specifically, the heat transfer fluid does not flow through stage 212 because the openings 206, 208, 222, and 224 corresponding to stage 212 when in positions 6, 7, and 8 are not aligned with any of the ports 240, 242, 244, or 246.

Referring to step 706 of FIG. 7, as regenerator housing 202 continues to rotate in the direction of arrow W, stage 212 will eventually reach position 1. As shown in FIGS. 3 and 6, at position 1 the heat transfer fluid in stage 212 can flow through the material as second inlet port 244 is now aligned with an opening 224 in second valve 216 and an opening 208 at the second end 220 while first outlet port 242 is aligned with an opening 222 in first valve 214 and opening 206 at first end 218. As indicated by arrow Q_(C-OUT), heat transfer fluid in stage 212, now cooled by the MCM, can travel out of regenerator housing 202 and along line 162 to the second heat exchanger 128. At the same time, and as indicated by arrow Q_(C-IN), heat transfer fluid from first heat exchanger 124 flows into stage 212 from line 160 when stage 212 is at position 5. Because heat transfer fluid from the first heat exchanger 124 is relatively warmer than the MCM in stage 212 at position 5, the MCM will be heated by the heat transfer fluid. The heat transfer fluid now travels along line 162 to the second heat exchanger 128 to receive additional heat.

As regenerator housing 202 is rotated continuously, the above described process of placing stage 212 in and out of magnetic field M is repeated. Additionally, the size of magnetic field M and regenerator housing 202 are such that a subset of the plurality of stages 212 is within the magnetic field at any given time during rotation. Similarly, a subset of the plurality of stages 212 are outside (or substantially outside) of the magnetic field at any given time during rotation. Additionally, at any given time, there are at least two stages 212 through which the heat transfer fluid is flowing while the other stages remain in a dwell mode. More specifically, while one stage 212 is losing heat through the flow of heat transfer fluid at position 5, another stage 212 is receiving heat from the flowing heat transfer fluid at position 1, while all remaining stages 212 are in dwell mode. As such, the system can be operated continuously to provide a continuous recirculation of heat transfer fluid in heat pump system 120 as stages 212 are each sequentially rotated through positions 1 through 8.

As will be understood by one of skill in the art using the teachings disclosed herein, the number of stages for housing 202, the number of ports in valve 214 and 216, and/or other parameters can be varied to provide different configurations of heat pump 200 while still providing for continuous operation. For example, each valve could be provided within two inlet ports and two outlet ports so that heat transfer fluid flows through at least four stages 212 at any particular point in time. Alternatively, regenerator housing 202, valves 222 and 224, and/or seals 236 and 238 could be constructed so that e.g., at least two stages are in fluid communication with an inlet port and outlet port at any one time. Other configurations may be used as well.

As stated, stage 212 includes MCM extending along the axial direction of flow. The MCM may be constructed from a single magneto caloric material or may include multiple different magneto caloric materials. By way of example, appliance 10 may be used in an application where the ambient temperature changes over a substantial range. However, a specific magneto caloric material may exhibit the magneto caloric effect over only a much narrower temperature range. As such, it may be desirable to use a variety of magneto caloric materials within a given stage to accommodate the wide range of ambient temperatures over which appliance 10 and/or heat pump 200 may be used.

A motor 130 is in mechanical communication with regenerator housing 202 and provides for rotation of housing 202 about axis A-A. By way of example, motor 130 may be connected directly with housing 202 by a shaft or indirectly through a gear box. Other configurations may be used as well.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

What is claimed is:
 1. A water heater appliance, comprising: a tank; a first heat exchanger coupled to the tank for delivery of heat to liquid within the tank; a second heat exchanger; and a caloric heat pump system configured for heating liquid within the tank at the first heat exchanger, the caloric heat pump system comprising a plurality of caloric material stages; a field generator positioned proximate the caloric material stages, the field generator positioned such that the caloric material stages are sequentially moved in and out of a field of the field generator during operation of the caloric heat pump system; and a pump for circulating a heat transfer fluid between the first and second heat exchangers and the caloric material stages.
 2. The water heater appliance of claim 1, wherein the tank extends between a top portion and a bottom portion along a vertical direction, an inlet of the first heat exchanger positioned at the bottom portion of the tank, an outlet of the first heat exchanger positioned at the top portion of the tank.
 3. The water heater appliance of claim 2, wherein the first heat exchanger comprises a conduit wound around the tank at an outer surface of the tank.
 4. The water heater appliance of claim 3, wherein the conduit of the first heat exchanger is wound around the tank between the inlet and the outlet of the first heat exchanger.
 5. The water heater appliance of claim 3, wherein adjacent windings of the conduit are spaced apart from one another along the vertical direction on the outer surface of the tank.
 6. The water heater appliance of claim 5, wherein the adjacent windings of the conduit are uniformly spaced apart from one another along the vertical direction on the outer surface of the tank.
 7. The water heater appliance of claim 3, wherein the conduit is wound onto the outer surface of the tank at a constant rate.
 8. The water heater appliance of claim 1, wherein the heat transfer fluid comprises water.
 9. The water heater appliance of claim 1, further comprising an electric heating element disposed within the tank and operable to heat liquid within the tank.
 10. The water heater appliance of claim 1, further comprising a casing, the tank, the second heat exchanger and the caloric material stages all disposed within the casing, the second heat exchanger and the caloric material stages positioned over the tank within the casing.
 11. A water heater appliance, comprising: a casing; a tank disposed within the casing; a first heat exchanger disposed within the casing and coupled to the tank for delivery of heat to liquid within the tank; a second heat exchanger disposed within the casing such that the second heat exchanger is spaced apart from the first heat exchanger; a caloric heat pump system disposed within the casing and configured for heating liquid within the tank via the first heat exchanger, the caloric heat pump system comprising a plurality of caloric material stages; a field generator positioned proximate the caloric material stages, the field generator positioned such that the caloric material stages are moved in and out of a field of the field generator during operation of the caloric heat pump system; and a pump for circulating an aqueous heat transfer fluid between the first and second heat exchangers and the caloric material stages.
 12. The water heater appliance of claim 11, wherein the tank extends between a top portion and a bottom portion along a vertical direction, an inlet of the first heat exchanger positioned at the bottom portion of the tank, an outlet of the first heat exchanger positioned at the top portion of the tank.
 13. The water heater appliance of claim 12, wherein the first heat exchanger comprises a conduit wound around the tank at an outer surface of the tank.
 14. The water heater appliance of claim 13, wherein the conduit of the first heat exchanger is wound around the tank between the inlet and the outlet of the first heat exchanger.
 15. The water heater appliance of claim 13, wherein adjacent windings of the conduit are spaced apart from one another along the vertical direction on the outer surface of the tank.
 16. The water heater appliance of claim 15, wherein the adjacent windings of the conduit are uniformly spaced apart from one another along the vertical direction on the outer surface of the tank.
 17. The water heater appliance of claim 13, wherein the conduit is wound onto the outer surface of the tank at a constant rate.
 18. The water heater appliance of claim 11, further comprising an electric heating element disposed within the tank and operable to heat liquid within the tank.
 19. The water heater appliance of claim 11, wherein the caloric material stages and the second heat exchanger are positioned over the tank within the casing. 